Scintillators are used widely in the detection and spectroscopy of energetic photons (e.g., x-rays and gamma rays). They are commonly used in nuclear and high energy physics research, medical imaging, and downhole logging operations (e.g., operations in which gamma ray measurements are used to determine properties of subterranean formations).
Single crystal Yttrium Aluminum Perovskite (e.g., YAlO3:Ce3+) is one promising scintillating material. However, such crystals are known to be characterized as having both a spatially non-uniform performance and a low transmittance due to the presence of color centers in the crystal. The color centers (F-centers and F+-centers) are believed to cause self-absorption of light emitted by the Ce3+ luminescence centers. The color centers may be concentrated in certain regions of the crystal (e.g., in the lower and internal portions of the crystal, for example as depicted on FIG. 1), depending on crystal growth conditions. Since light output efficiency is an important scintillator property, the presence of the color centers tends to limit the utility of Yttrium Aluminum Perovskite scintillators. Moreover, the presence of the color centers limits the size of the crystal scintillators that may be utilized. In an attempt to overcome this difficulty very thin crystals have been utilized in the prior art. For example, Zeng et al (Effects of Annealing on the Color, Absorption Spectra, and Light Yield of Ce:YAlO3 Single Crystal Grown by the Temperature Gradient Technique, Journal of Applied Physics 95(2), 749, 2004) utilized crystals having a thickness of 1 mm and Cao et al (Effects of Growth Atmosphere and Annealing on Luminescence Efficiency of YAP:Ce Crystal, Journal of Alloys and Compounds 489, 515, 2010) utilized crystals having thicknesses of 0.36 and 2 mm. At thicknesses greater than about 5 mm annealing has not been previously shown to effectively remove color centers and other defects from the crystals.
Therefore a need remains in the art for improved Yttrium Aluminum Perovskite scintillators and methods for fabricating such scintillators.